The outer surface of steel pipe, when used in an outdoor application, is generally provided with a corrosion resistant coating, such as fusion bonded epoxy. When the pipe is buried in the ground, for instance, at underground road crossings, the pipe is generally further protected by being enclosed within a tubular metallic casing. The pipe is supported within the casing by a pipeline casing insulator. The casing insulator, in addition to its supportive function, electrically insulates the pipe from the casing. This insulative function is necessary for the cathodic protection of the pipe, and also, for preventing current loss when the pipe is used as a conduit for electrical cables. Furthermore, the casing insulator prevents damage to the outer coated surface of the pipe when the pipe is drawn through the casing during installation.
The prior art pipeline casing insulators include a rigid steel band that encircles the outer coated surface of the pipe. The inner surface of the band is lined with an electrically insulating, oil resistant, rubber liner that contacts the coated surface of the pipe. A plurality of runners are connected to the outer surface of the band to support the pipe within the casing. The band is formed from a pair of sections that are bolted together to connect the band to the pipe. An example of a prior art pipeline casing insulator, as generally described above, is illustrated in Pipeline Casing Insulators, Casing End Seals and Wall Penetration Seals, Section 100, Bulletin No. 14825 12/85, Maloney Pipeline Products Co. of 5200 Cedar Crest, Houston, Tex. 77087.
As can be appreciated, the band, the rubber liner, the runners and the mounting hardware are provided as separate components that are relatively expensive and that require time consuming field assembly. Moreover, the metallic components of the prior art casing insulator can damage the integrity of the corrosion resistant coating during assembly.
The present invention provides a pipeline casing insulator that is less expensive than the prior art casing insulators and that, also, requires no field assembly. A casing insulator fabricated in accordance with the present invention accomplishes these advantages by utilizing a flexible belt of, preferably, an organic non-woven material, in place of the rigid band and liner structure of the prior art, and a plurality of elongated runners that are preferably formed from a polymer concrete that is cast directly onto the band. In a preferred embodiment, the belt is connected to the pipe by a precoating of mastic that is applied to one of the surfaces of the belt. The mastic, prior to installation, is covered by a release strip which is removed when attaching the belt to the pipe. As is evident, this structure is inexpensive to manufacture and requires no extensive assembly. Additionally, the structure contains no metal parts that could damage the pipe coating during attachment.